# 1260. Shift 2D Grid

###### tags: `leetcode`,`easy`

>ref: https://leetcode.com/problems/shift-2d-grid/
>
Given a 2D grid of size m x n and an integer k. You need to shift the grid k times.

In one shift operation:

Element at grid[i][j] moves to grid[i][j + 1].
Element at grid[i][n - 1] moves to grid[i + 1][0].
Element at grid[m - 1][n - 1] moves to grid[0][0].
Return the 2D grid after applying shift operation k times.



>Constraints:
m == grid.length
n == grid[i].length
1 <= m <= 50
1 <= n <= 50
-1000 <= grid[i][j] <= 1000
0 <= k <= 100

>1. mod(m\*n) list收集n元素後 用新的list收集n元素 直到收集m\*n個元素
>2. time O(n) spatial O(n)

    public List<List<Integer>> shiftGrid(int[][] grid, int k) {
        
        int m=grid.length;
        int n=grid[0].length;
        
        k=(m*n)- k%(m*n);
        
        List<List<Integer>> res= new LinkedList<>();
        
        int row_count=0;
        List<Integer> row= new LinkedList<>();
        
        for(int a=0 ; a < m*n ; a++){
            k%=(m*n);
            int i= k/n;
            int j= k%n;
            k++;
            
            row.add(grid[i][j]);
            
            if(row_count++ == n-1){
                res.add(row);
                row= new LinkedList<>();
                row_count=0;
            }
        }
        
        return res;
        
    }